#!/usr/bin/env perl

# value: referce to a node and node have two values: data, next link addr ie [DATA, pointer]
my @node_ref; 

foreach (0 .. 5){
#foreach ('a' .. 'm'){
 my $ref = [$_, undef]; #  assign value as an anonymous array reference
 push @node_ref, $ref;
}
#0 node0 refeence
#1 node1 refeence
#2 node2 refeence
#3 node3 refeence
#4 node4 refeence
#5 node5 refeence

my $head=['iam_headValue_and_iam_NOT_important', undef];

# link all data together
foreach my $index (0 .. @node_ref-1){
 if ($index == 0) {
  $head->[1] = $node_ref[0];
  next;
 }
 else {
  $node_ref[$index-1]->[1] = $node_ref[$index];
 }
}
# head -> firstNode -> secondNode -> 3rdNode ... ->NULL (end)

my $cur=$head;

# traverse
while ($cur->[1]){
 print "$cur->[0] ";
 $cur = $cur->[1];
}

print $cur->[0], "\n"; #last one value since traverse ended when last ref hit